Pulse width modulation valve control for vital sign monitors

Abstract

A method for measuring a patient's blood pressure involves using a patient-applied cuff operably connected to an electronically controlled blood pressure monitor that includes a pump. The method includes controlling pressure in the cuff by inflating the cuff to a suprasystolic pressure, and step-wise deflating of the cuff to acquire blood-pressure data from the patient. The improvement includes using pulse-width modulation data to enhance control of cuff pressure.

I claim: 
     
       1. A method for measuring a patient's blood pressure that involves using a patient-applied cuff operably connected to an electronically controlled blood pressure monitor including a pump, controlling pressure in the cuff by inflating the cuff to a suprasystolic pressure, and step-wise deflating of the cuff to acquire blood-pressure data from the patient, the improvement comprising: choosing a digital valve to control inflating and deflating of the patient-applied cuff   coupling the valve to the pump and including a port in the valve that is set to be open;   determining that fluid flow increases as the duty cycle of the pump increases, that fluid flow decreases as the drive frequency of the pump increases, and that flow is inversely proportional to the drive frequency of the pump and proportional to the duty cycle of the pump;   evaluating the performance of the digital valve; and   using the information from the determining and evaluating steps to select a desired fluid flow curve for the pump.